-lactoglobulina em biscoitos semidoces: estudo de degradação no processamento e potencial antigênico, validação de método e avaliação da rotulagem

Abstract

The -lactoglobulin (LG) is the most abundant whey protein and plays an important role in allergy to cow's milk (CMA) that represents the most common food allergy in children -the largest consumer of biscuits. Despite the analysis of labeling and the development of methodologies for determination of allergens in foods constitute fundamental tools for the control of CMA, studies related to these topics are restricted in the literature. Also, it is known that the thermal processing promotes conformational changes in allergenic proteins, although the literature is controversial about the impact on the antigenic potential. The objective of this work was to evaluate the degradation and antigenicity of the LG in processed biscuits, to validate a commercial ELISA kit for the determination of this protein in biscuits and to evaluate the labeling of semi-sweet biscuits from Minas Gerais, Brazil. Semi-sweet biscuits with 0.25% milk were cooked under different conditions of temperature (150, 180 and 210 °C) and time (5, 10, 15, 20, 25 and 30 minutes) and analyzed by ELISA in duplicate. For validation, biscuits formulated without milk and spiked with LG standard at 0.25 mg/kg to 13.5 mg/kg, plus the unspiked sample, were analyzed by ELISA kit, being 20 replicates per level. The labeling of eighteen semi-sweet biscuits commercial samples was analyzed. Significant reduction in LG content and, consequently, in the antigenicity was observed with 15 minutes of baking for all studied temperatures (p < 0.05). The reduction reached 89.7, 92.6 and 100 % for 150, 180 and 210 °C, respectively. The kit was considered adequate for the purpose of LG detection, although it has not shown satisfactory performance in a quantitative validation approach. Selectivity rate of 100% was estimated for the samples without the analyte. Sensitivity rates of 70 80 and 100% were calculated for the levels 0.25; 0.5; and from 1.0 mg/kg, respectively. The method was considered standardized with accordance values between 0.5 and 1.0 and concordance between 0.7 and 1.0, with maximum values achieved for the level 0 mg/kg and from level 1.0 mg/kg. Selectivity was demonstrated for ovalbumin as interferent. In labeling analysis a reduction in the percentage of non-conformity was identified for 2016 when compared to 2014-2015, while 22.2% of the labels analyzed in 2016 were not compliant to the regulation of allergens.